Monolithically Integrated Waveguide Sensors on Diamond Display Glass System and Method

ABSTRACT

A transparent display includes a display including a transparent substrate and a patterned diamond layer formed on the transparent substrate to at least in part define a diamond waveguide. At least two electronic devices can be connected by the diamond waveguide, and can include a sensor, a transducer, or electronic circuitry, including communication, control, or data processing electronic circuitry.

RELATED APPLICATION

The present disclosure is part of a non-provisional patent applicationclaiming the priority benefit of U.S. Provisional Patent Application No.63/131,541, filed on Dec. 29, 2020, which is incorporated by referencein its entirety.

TECHNICAL FIELD

The present disclosure relates generally to the field of materials andcoatings that support transparent diamond optoelectronics. Morespecifically, described are systems and methods for integrating sensorsinto a multi-layer diamond display system such as can be used inelectronic devices.

BACKGROUND

Diamond possesses favorable optical, mechanical, and semiconductorperformance characteristics, enabling the possibility of creatingtransparent electronics and opto-electronics including those related toconsumer electronic components and materials such as displays and lensmaterials. These applications often include stringent designrequirements such as increased hardness, scratch resistance, and waterresistance. These applications also often require the use of integratedsensing components (e.g., thermal, biological, and chemical). Althoughdiamond is well suited to addressing these stringent design requirementsand functionality, practical applications for consumer electronics havebeen limited due to manufacture costs or process limitations. Materials,structures, and procedures that reduce or eliminate such issues areneeded.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present disclosureare described with reference to the following figures, wherein likereference numerals refer to like parts throughout the various figuresunless otherwise specified.

FIG. 1 is a schematic diagram of an exemplary display glass systemhaving integrated optical waveguide structures for integrating sensors;

FIG. 2 is an embodiment of a method for fabricating a display glasssystem having integrated diamond waveguides for integrating sensors; and

FIG. 3 is an embodiment of a method for fabricating a display glasssystem having optical waveguides with polycrystalline and/ornanocrystalline diamond coating.

DETAILED DESCRIPTION

Consumer and industrial electronics are increasingly incorporating awide variety of sensors and transducers to enhance the users'experience. As an example, modern mobile telephones often incorporatesensors for temperature (e.g., to protect circuitry), medical (e.g.,heart rate), and chemical (e.g., liquids such as water) purposes. Otherelectronic devices extensively incorporating sensors include but are notlimited to virtual reality headsets, protective face shields, heads-updisplays, cameras, and televisions. Example environmental sensors andtransducers that have or are envisioned to be integrated into mobilephones and other devices can include those responding to visible light,infrared light, temperature, detected chemicals, proximity, or pressure.Example biological sensors can include monitors for heart rate, bloodoxygen, blood pressure, fingerprints, galvanic skin response, EEG/EKG,or brain waves. Example electromechanical sensors or transducers caninclude speakers, microphones, gyroscopes, accelerometers, wirelesspower, photonic power, or quantum security components.

Many of these sensors and transducers can be embedded in passive oruser-interactive displays. Likewise, communication links betweensensors, transducers, and external circuitry can be embedded in thedisplays. To maintain a quality user experience, these sensors,transducers, and communication links between can be made transparent tovisible light. Transparent optical waveguides embedded in the displaysystem can and are expected to facilitate these communication links.

Advantageously, diamond has broad optical transmissivity over thevisible light spectrum, thus enabling its use as a protective coating ondisplay glasses. Diamond is known to have useful physical properties,such has extreme hardness and thermal conductivity, that can improvedisplay glass scratch resistance and temperature management. Otherdiamond properties such as hydrophobicity and chemical/biologicalinertness also make it highly desirable as a protective coating ondisplay glasses. Multilayer combinations of diamond and other materials,including other carbon compounds, can further enhance these properties.

This disclosure describes the use of diamond to enable transparentoptical waveguides for integration of sensors and transducers in moderndisplay systems. In this invention, diamond is used as an opticalwaveguide, a protective coating for a glass optical waveguide, and/or asurface protectant for a display system. Disclosed herein is a new andimproved system and method for integrating sensors into diamond coatedoptically transparent display glass systems. In accordance with oneaspect of the approach, an optically transparent display glass systemwith integrated sensors may include an optically transparent single(e.g., alumino-silicate) or multilayer glass substrate. In oneembodiment, polycrystalline diamond, nanocrystalline diamond (i.e. withgrain sizes less than about 100 nm), or a combination of polycrystallineand nanocrystalline diamond can be included in a diamond film coatingthe glass substrate, and in optical waveguides formed in the diamondfilm coating. In effect, display structures that are low cost, durable,and useful can include at least two electronic devices that are at leastone of a sensor, a transducer, or electronic circuitry, includingcommunication, control, or data processing electronic circuitry. Theelectronic devices can be connected by the diamond waveguide transparentsubstrate and a patterned diamond layer formed on the transparentsubstrate to at least in part define a diamond waveguide.

In accordance with another aspect of the approach, a method offabricating an optically transparent display glass system may includethe steps of (1) selecting a single or multilayer glass substrate, (2)cleaning and seeding the substrate, (3) forming a diamond film includingpolycrystalline and/or nanocrystalline diamond on the glass substrateusing a chemical vapor deposition system having a reactor in whichmethane, hydrogen, and argon source gases are added, (4) patterningoptical waveguide structures using semiconductor lithography, and (5)forming optical waveguide structures in the diamond using reactive ionetching.

In another embodiment, a method for forming a transparent displayincorporating a waveguide includes providing a transparent substrate andforming a diamond film including polycrystalline and/or nanocrystallinediamond on the transparent substrate. Optical waveguide structures inthe diamond film can also include polycrystalline and/or nanocrystallinediamond and can be patterned by etching, with the optical waveguidestructures able to interconnect least two electronic devices.

U.S. Pat. Nos. 10,254,445 and 10,224,514 are incorporated by referenceand include information on the use and deposition of diamond on glasssuitable for use in conjunction with described systems and methods.Patent application U.S. Ser. No. 17/031,762 is also incorporated byreference and includes information on the deposition of diamond andfluorinated graphene oxide suitable for use in conjunction withdescribed systems and methods.

Other systems, methods, aspects, features, embodiments, and advantagesof the system and method disclosed herein will be, or will become,apparent to one having ordinary skill in the art upon examination of thefollowing drawings and detailed description. It is intended that allsuch additional systems, methods, aspects, features, embodiments, andadvantages be included within this description, and be within the scopeof the accompanying claims.

FIG. 1 illustrates an exemplary display glass system 100 havingintegrated optical waveguide structures for integrating sensors. In thisexample, the display glass system is integrated into a mobile telephone.The display glass system 100 can include a single or multilayersubstrate 110 that includes a diamond layer 112. Optionally, one or moreadditional layers that enhance the surface properties of the display canbe included above or below the diamond layer 112, all layers of whichare transparent to visible light. The display glass system 100 mayinclude sensors and transducers 120, 122, 124, and 126 embedded in, on,or beneath the transparent layers of the system. The display glasssystem 100 can also include transparent optical waveguides 130, 132,134, and 136 that interconnect the embedded sensors and transducers 120,122, 124, and 126 and any associated optoelectronic circuitry externalto the display system. The substrate, diamond layer 112, and optionalenhancement layers may be curved at the edges to facilitate “wraparound”communications via waveguides that follow the contour of the curvedsurface.

The single or multilayer substrate may be composed of glass, includingalumno-silicate (chemically or non-chemically hardened), silicate,soda-lime, borosilicate, germinate, phosphate, fluoride, or chalcogenideglasses, display plastics, or other transparent materials know to thosehaving ordinary skill in the art. Any of the aforementioned materials,as well as combinations thereof, may be included in the substrate layer.

In some embodiments, the diamond layer 112 can include coatings ofvarious diamond, diamond-like, or diamond containing materials andstructures. For the purposes of this disclosure, diamond refers to acrystalline structure of carbon atoms bonded to other carbon atoms in alattice of tetrahedral coordination known as sp³ bonding. Each carbonatom can be surrounded by and bonded to four other carbon atoms, eachlocated on the tip of a regular tetrahedron. In some embodiments thetetrahedral bonding configuration of carbon atoms can be irregular ordistorted for at least some volume of the diamond layer 112, orotherwise deviate from the standard tetrahedron configuration of diamondas described above. Such distortion generally results in lengthening ofsome bonds and shortening of others, as well as the variation of thebond angles between the bonds. In some embodiments, the distortion ofthe tetrahedron alters the characteristics and properties of the carbonto effectively lie between the characteristics of carbon bonded in sp³configuration (i.e. diamond) and carbon bonded in sp² configuration(i.e. graphite). One example of material having carbon atoms bonded indistorted tetrahedral bonding is amorphous diamond. In other diamondfilm embodiments, diamond-like carbon can be formed as a carbonaceousmaterial having carbon atoms as the majority element, with some amountof such carbon atoms bonded in distorted tetrahedral coordination.Diamond films can include a variety of other elements as impurities oras dopants, including without limitation, hydrogen, sulfur, phosphorous,boron, nitrogen, silicon, or tungsten. This can be useful, for example,in modifying electrical or chemical diamond film properties.

Diamond deposition can be by any process such as, but not limited to,chemical vapor deposition (CVD) and physical vapor deposition (PVD). Awide variety of embodiments of vapor deposition method can be used.Examples of vapor deposition methods include hot filament CVD, rf-CVD,laser CVD (LCVD), laser ablation, conformal diamond coating processes,metal-organic CVD (MOCVD), sputtering, thermal evaporation PVD, ionizedmetal PVD (IMPVD), electron beam PVD (EBPVD), reactive PVD, cathodicarc, and the like.

In some embodiments, a thin diamond film can be deposited at relativelylow temperatures of less than 570 degrees Celsius using an activationmedium like plasma, argon gas and a carbon source, such as methane. Inother embodiments, deposition can be at temperatures between 375 and 500degrees Celsius. Advantageously, as compared to conventional 700-800degree Celsius temperatures for diamond film growth, such lowtemperatures greatly reduce thermal warping of a substrate or otherapplied coatings, or associated electronics or optoelectronics. In otherembodiments, the diamond layer 112 can be a thin film polycrystallinediamond deposited at a low temperature to eliminate or minimizedegradation of substrate glasses, embedded electronics, or embeddedopto-electronics, for example, at temperatures less than 450 degreesCelsius. In one embodiment, the diamond layer may be approximately 500nm thick to support fabrication of optical waveguides in the layer. Inanother embodiment, the diamond layer may be approximately 100 nm thickto serve as a surface protectant for the underlying glass layer andoptical waveguides fabricated therein.

In some embodiments, deposition gas is ignited and forms small diamondsthat grow on a wafer, producing a continuous, thin, and conformal layer.The type and structure of diamond deposited is dependent on the seedmethod used. Large grain seed can result in microcrystalline diamondwith increased hardness. Small grain sizes in nanocrystalline diamond(typically less than 100 nm) can provide lower surface roughness.

Properties of diamond film can be measured and characterized using Ramanspectroscopy. Cubic diamond has a single Raman-active first order phononmode at the center of the Brillouin zone. The presence of sharp Ramanlines allows cubic diamond to be recognized against a background ofgraphitic or other carbon crystal types. Small shifts in the bandwavenumber can indicate diamond composition and properties. In someembodiments, the full width half maximum (FWHM) obtained from Ramancharacterization for the diamond films formed as indicated in thisdisclosure can be between 5-10.

In some embodiments the diamond film can be conformally deposited overas a continuous layer over the surface. Alternatively, with the use ofmasking, etching, or suitable growth enhancing or growth reducingtechniques, only selected area(s) can be provided with a diamond film.In some embodiments, diamond film thickness can be constant across thesurface, while in other embodiments thickness can vary according toposition.

In some embodiments, diamond film thickness can be constant across thesurface, while in other embodiments thickness can vary according toposition. Diamond thickness can be between 10 nanometers to 100 microns.In some embodiments, grain size can be between 200 and 300 microns. Insome embodiments, at least 95% of the grains are sized between 200 and300 microns. In still other embodiments, at least 99% of the grains aresized between 200 and 300 microns.

An additional thin film material (e.g., fluorinated graphene oxide) maybe included on the diamond layer to further enhance surface properties(e.g., hydrophobicity) of the display. This additional layer may be acarbon-based compound or other material.

The sensors and transducers 120, 122, 124, and 126 embedded in, on, orbeneath the transparent layers of the display system 100 can befabricated with transparent opto-electronic circuitry. The circuitry maybe fabricated in a semiconducting diamond layer 112 with doped regionsthat modify electrical characteristics. The sensors and transducers 120,122, 124, and 126 can communicate through optical receive and/ortransmit interfaces via the optical waveguide structures embedded in thediamond layer 112 or substrate layers of the display system 100.Interfaces to sensor and transducers 120, 122, 124, and 126 can be usedto receive control signals, transmit data, receive power, or facilitateother communication between sensors, transducers, computers,controllers, other circuitry in the device, and external circuitry.

The optical waveguides 130, 132, 134, and 136 can be formed in the thinfilm diamond coating layer or in the underlying glass layer that issubsequently coated with a protective diamond thin film. The waveguidestructures may be rectangular in cross section with, for example,dimensions less than 1 um to facilitate optical communication in the lowinfrared range. The waveguide structures may follow straight or curvepaths. Waveguides may also “wrap around” the curved edges of the displaysystem to facilitate communication to external optoelectronics in theunderlying or adjacent. The bend radius of the optical waveguides maybe, for example, less and 0.5 mm without causing excessive transmissionloss.

FIG. 2 illustrates one embodiment of a process 200 for manufacture of adiamond optical waveguides on a glass substrate. The fabrication of themultilayer structure can be realized by utilizing a combination oftechniques, such as, chemical vapor deposition (CVD), physical vapordeposition (PVD), lithography which can be e-beam or optical lithographyand reactive ion etching (RIE).

The glass substrate can be of any type of glass such as alumino-silicate(chemically hardened and non-chemically hardened), fused silica,silicate glass, soda-lime glass, borosilicate glasses, germanateglasses, phosphate glasses, fluoride glasses, chalcogenide glasses,filter & attenuator glasses, crown & flint glasses, and foldableplastic, based on the application and environment of operation.

The selected glass substrate can be cleaned by exposing to an acidcleaning mixture, such as (4:1 H₂SO₄/H₂O₂, 5:1:1 H₂O/H₂O₂/HCl) and abuffered oxide etch, to remove surface contaminants and oxides.Furthermore, the substrate is subjected to an alcohol based ultrasoniccleaning. The next step involves seeding the glass substrate with ananoseed solution mixture and ultrasonication in alcohol solution topromote nucleation and film agglomeration.

To form layer structure 210 of process 200, polycrystalline diamond isgrown on glass using hot filament chemical vapor deposition (HF-CVD) ormicrowave plasma CVD growth process that contains methane, hydrogen, andargon gas mixtures, where the diamond deposition is in the order of afew hundred nanometers per hour. In the event that the diamond growth isbeyond the target thickness, reactive ion etching via an argon andoxygen mixture and/or ion milling may produce bulk, planarized, uniform,diamond films. The diamond surface may also be polished to minimizesurface roughness and improve transmission of subsequently formeddiamond waveguides.

To form layer structure 220 of process 200, allowing fabrication ofoptical waveguides on diamond, initially a 15 nm layer of Al isdeposited by sputtering or evaporation technique. Hydrogensilsesquioxane (HSQ), which is a negative e-beam resist is then spincoated on to the Al layer to form layer structure 230 of process 200. Toform layer structure 240 of process 200, e-beam lithography is performedand developed to pattern the optical waveguides. The waveguides can havea width varying between 100 to 700 nm. The HSQ acts as mask for etchingthe Poly Crystalline Diamond (PCD) using reactive ion etching (ME) withoxygen and argon plasma. 400 nm PCD is etched in a controlled mannerforming the waveguides and ensuring the presence of the remaining 100 nmdiamond layer to form a rib waveguide structure. The HSQ and Al layerscan be removed using any of the etching techniques, either by plasmaetching or wet etching methods (e.g., using buffered oxide etch).

An additional thin film material (e.g., fluorinated graphene oxide) maybe included on the diamond layer to further enhance surface properties(e.g., hydrophobicity) of the display. This additional layer may be acarbon-based compound or other material. The methodology for depositionof this layer can be found in patent application U.S. Ser. No.17/031,762 previously incorporated by reference and which includesinformation on the deposition of diamond and fluorinated graphene oxidesuitable for use in conjunction with described systems and methods.

In some embodiments, the entire multilayer glass, diamond, diamondwaveguide, and FGO structure may subjected to a thermal bending processto form, for example, a waterfall-style screen with an approximately 88degree bend angle.

FIG. 3 illustrates one embodiment of a process 300 for manufacture of adiamond optical waveguides. The fabrication of the multilayer structurecan be realized by utilizing a combination of techniques, such as,chemical vapor deposition (CVD), physical vapor deposition (PVD),lithography which can be e-beam or optical lithography and reactive ionetching (ME).

The glass substrate can be of any type of glass such as alumino-silicate(chemically hardened and non-chemically hardened), fused silica,silicate glass, soda-lime glass, borosilicate glasses, germanateglasses, phosphate glasses, fluoride glasses, chalcogenide glasses,filter & attenuator glasses, crown & flint glasses, and foldableplastic, based on the application and environment of operation.

Process 300 can involve exposing a selected substrate to an acidcleaning mixture, such (4:1 H₂SO₄/H₂O₂, 5:1:1 H₂O/H₂O₂/HCl) and abuffered oxide etch, to remove surface contaminants and oxides.Furthermore, the substrate is subjected to an alcohol based ultrasoniccleaning.

To form layer structure 310 of process 300 useful for fabrication ofoptical waveguides on glass, initially a 50 nm layer of Cr is depositedby sputtering or evaporation technique to act as mask for pattering thewaveguides. To form layer structure 320 of process 300, hydrogensilsesquioxane (HSQ) or similar negative e-beam resist is then spincoated on to the Cr layer. To form layer structure 330 of process 300,lithography, such as E-beam lithography, is performed and developed topattern the optical waveguides. The waveguides have a width varyingbetween 100 to 700 nm. The Cr acts as mask for etching the glass usingreactive ion etching (RIE) with CF4/CHF3 plasma. 400 nm of glass isetched in a controlled manner forming the waveguides forming a ribwaveguide structure. To form layer structure 340 of process 300, theresidual HSQ and Cr layers can be removed using any of the etchingtechniques, either by plasma etching or wet etching methods (e.g., usingbuffered oxide etch).

To form layer structure 350 of process 300, a next step involves seedingthe substrate with a nanoseed solution mixture and ultrasonication inalcohol solution to promote nucleation and film agglomeration.Polycrystalline diamond 352 is grown on glass using hot filamentchemical vapor deposition (HF-CVD) or microwave plasma CVD growthprocess that contains methane, hydrogen, and argon gas mixtures, wherethe diamond deposition is in the order of a few hundred nanometers perhour.

An additional thin film material (e.g., fluorinated graphene oxide) maybe included on the diamond layer to further enhance surface properties(e.g., hydrophobicity) of the display. This additional layer may be acarbon-based compound or other material. The methodology for depositionof this layer can be found in patent application U.S. Ser. No.17/031,762 previously incorporated by reference and which includesinformation on the deposition of diamond and fluorinated graphene oxidesuitable for use in conjunction with described systems and methods.

In some embodiments, the entire multilayer glass, diamond, diamondwaveguide, and FGO structure may subjected to a thermal bending processto form, for example, a waterfall-style screen with an approximately 88degree bend angle.

In the foregoing description, reference is made to the accompanyingdrawings that form a part thereof, and in which is shown by way ofillustration specific exemplary embodiments in which the disclosure maybe practiced. These embodiments are described in sufficient detail toenable those skilled in the art to practice the concepts disclosedherein, and it is to be understood that modifications to the variousdisclosed embodiments may be made, and other embodiments may beutilized, without departing from the scope of the present disclosure.The foregoing detailed description is, therefore, not to be taken in alimiting sense.

Reference throughout this specification to “one embodiment,” “anembodiment,” “one example,” or “an example” means that a particularfeature, structure, or characteristic described in connection with theembodiment or example is included in at least one embodiment of thepresent disclosure. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” “one example,” or “an example” invarious places throughout this specification are not necessarily allreferring to the same embodiment or example. Furthermore, the particularfeatures, structures, databases, or characteristics may be combined inany suitable combinations and/or sub-combinations in one or moreembodiments or examples. In addition, it should be appreciated that thefigures provided herewith are for explanation purposes to personsordinarily skilled in the art and that the drawings are not necessarilydrawn to scale.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims. It is also understood that other embodiments of this inventionmay be practiced in the absence of an element/step not specificallydisclosed herein.

1. A transparent display, comprising: a display including a transparentsubstrate and a patterned diamond layer formed on the transparentsubstrate to at least in part define a diamond waveguide; and at leasttwo electronic devices connected by the diamond waveguide.
 2. Thetransparent display of claim 1, wherein the at least two electronicdevices are at least one of a sensor, a transducer, or electroniccircuitry, including communication, control, or data processingelectronic circuitry.
 3. The transparent display of claim 1, wherein thetransparent substrate is a glass.
 4. The transparent display of claim 1,wherein the patterned diamond layer is formed at temperatures of lessthan 570 degrees Celsius.
 5. The transparent display of claim 1, whereinthe patterned diamond layer is formed to continuously cover the display.6. The transparent display of claim 1, wherein the patterned diamondlayer has a thickness of less than 500 microns.
 7. The transparentdisplay of claim 1, wherein the display is bent at an angle.
 8. A methodfor forming a transparent display incorporating a waveguide, comprisingproviding a transparent substrate; forming a diamond film includingpolycrystalline and/or nanocrystalline diamond on the transparentsubstrate, and patterning optical waveguide structures in the diamondfilm by etching, with the optical waveguide structures able tointerconnect least two electronic devices.
 9. The method of claim 8,wherein the at least two electronic devices are at least one of asensor, a transducer, or electronic circuitry, including communication,control, or data processing electronic circuitry.
 10. The method ofclaim 8, wherein the transparent substrate is a glass.
 11. The method ofclaim 8, wherein the diamond film is formed at temperatures of less than570 degrees Celsius.
 12. The method of claim 8, wherein the diamond filmis formed to continuously cover the transparent display.
 13. The methodof claim 8, wherein the diamond film has a thickness of less than 500microns.
 14. The method of claim 8, wherein the transparent display withincorporated waveguide is bent at an angle.